Shell and tube heat exchangers, of the kind where water flows through a plurality of tubes in heat transfer relationship with a refrigerant on the shell side, are often used as evaporators and condensers, along with at least one compressor and other components to create an assembled water chilling unit. As an assembly, the changing of one component often has an impact on the other structure. For example, the evaporator may serve as the support for the compressor or condenser.
Another general constraint in chiller design is to have an even number of passes on the waterside so that all of the water connections can be located at one end of the heat exchanger shell, thus permitting the cleaning or servicing of the tubes from the other end without disturbing the water connections.
There are occasions where it is desired to reduce heat exchanger size to meet a given set of thermal and pressure drop requirements, yet such a reduction of the exchanger shell may not be possible due to the interrelationship of the various components of the chiller. For example, to match desired performance characteristics, it may be desirable to use a short length condenser shell with in combination with a long length cooler shell, but the chiller assembly would be compromised as a result.